Mechanism of orthoexciton-to-paraexciton conversion inCu2O

Abstract

The mechanism for conversion between the orthoexciton state and the lower-lying paraexciton state in ${\mathrm{Cu}}_2$O has never been completely understood. We propose that at low density this conversion takes place via the emission or absorption of a single acoustic phonon. We show that the rates derived using this mechanism give good agreement with the measured down-conversion rate as a function of temperature, as well as with the measured luminescence intensities of the orthoexcitons and paraexcitons as functions of temperature and stress.